Conduction, convection and radiation Cambridge IGCSE Physics (9–1) revision
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In plain words
Heat moves from hot to cold in three ways. Conduction: passed along from particle to particle, best in metals. Convection: a warm liquid or gas rises and cooler stuff sinks to take its place. Radiation: infrared waves that need nothing to travel through, which is how the Sun warms us across empty space.
Three things to know
- Conduction: energy passes from particle to particle. Metals are good conductors because they have free electrons; air and plastics are poor conductors (insulators).
- Convection: a warmed fluid expands, becomes less dense and rises; cooler fluid sinks to replace it. It only happens in liquids and gases.
- Radiation: infrared waves, which need no medium. Dull black surfaces are the best emitters and absorbers; shiny white ones the worst.
Tips and tricks
- Convection can't happen in a solid, because the particles can't flow. Radiation is the only one that works through a vacuum.
- Dull black surfaces are the best absorbers and emitters of radiation. Shiny white ones are the worst.
It lands in your notebook with its questions as flashcards.
Conduction, convection and radiation: 6 questions and answers
These are the quiz’s questions. Do the quiz first, then come back here for the ones that got you.
How is energy transferred through a metal rod?
Vibrating particles and free electrons pass the energy along.
Why is a vacuum a good insulator?
Conduction and convection both need a medium.
Which surface is the best emitter of infrared radiation?
Dull black surfaces emit and absorb best.
Why does hot air rise?
Warm air expands, so the same mass fills a bigger volume.
Which method of energy transfer can happen through empty space?
Infrared is an electromagnetic wave and needs no medium.
Why are metals better conductors than non-metals?
Free electrons move through the metal, transferring energy quickly.
Quiz
6 questions
Tap an answer and you’ll see straight away whether it’s right, and why.
Worksheet
4 questions, 9 marks. Write your answers on paper, then check them.
Conduction, convection and radiation
Cambridge IGCSE Physics (9–1) 0972 · 9 marks · papermunch.org
Name ______________________________ Date ______________
Explain why a saucepan has a metal base but a plastic handle.[2]
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Metal conducts energy well to the food; plastic is an insulator, so the handle stays cool.
Explain how a heater at the bottom of a room warms the whole room.[3]
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It warms the air near it, which expands, becomes less dense and rises. Cooler air sinks to take its place, setting up a convection current.
Explain why energy from the Sun cannot reach the Earth by conduction or convection.[2]
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Both need particles, and space is a vacuum. Only radiation can cross it.
Explain why houses in hot countries are often painted white.[2]
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White surfaces are poor absorbers of infrared radiation, so the house takes in less energy.
Answers: Conduction, convection and radiation
- 1. Metal conducts energy well to the food; plastic is an insulator, so the handle stays cool.
- 2. It warms the air near it, which expands, becomes less dense and rises. Cooler air sinks to take its place, setting up a convection current.
- 3. Both need particles, and space is a vacuum. Only radiation can cross it.
- 4. White surfaces are poor absorbers of infrared radiation, so the house takes in less energy.